Setting up Digital torch height control on your Z axis

jeepsr4ever

Those with the single controller box will use the terminal marked in red for the Z torch height control.

YOU MUST ACTIVATE Z AXIS HOME SWITCH IN MACH 3 FOR DTHC TO WORK. UNDER PORTS AND PIN IN THE CONFIG TAB. MAKE SURE Z HOME IS ACTIVATE AND TEST Z AXIS LIMIT SWITCH USING THE DIAGNOSTICS TAB IN MACH 3. IF Z HOME DOESNT LIGHT UP NOT WHICH LIMIT DOES LIGHT UP AND CHECK IT IN PORTS AND PINS AND SWITCH Z AXIS TO THAT LIMIT SWITCH (PORT AND PIN)[/b]

Creepy

where in mach3 do you put in the floating head travel offset? - ie - when the switch makes, and you zero Z, Z-home will be below the work instead of on the surface. where do you put that distance? (offsetting the Z home up)

jeepsr4ever

You can zero Z any place above the work piece. Sheetcam will control the pierce height and cutting height but tip volts will also control cutting height.

Creepy

that's not making any sense to me. Why have the switch if you just zero somewhere above the work? the sheetcam dthc post processor will touch the work to zero-out Z before starting the cut. without a Z axis offset equalling the floating head travel to make the switch, the controller will think Z zero is below the work. i found and added -.253" to the Z-home as an offset. Its under config/limits and homes. I'm still trying to get the DTHC to work, don't have an "ark ok" signal yet, but I have been cutting with a locked Z height above the work. The Z-offset was critical to this working if using the Z-switch as a home. Am i missing something?

jeepsr4ever

How DTHC works is you first touch off the material and then the head raises to pierce height a relay on the DTHC card kicks on the plasma cutter. When it is done piercing it will lower to cut height. Once this is established then DTHC kicks in maintaining that height throughout the cut adjusting the Z to the voltage setting you select in Mach 3. This gives you the best possible quality along the whole length of the cut.

Creepy

the initial touch to set the work height is the issue I'm working on. I understand the DTHC operation once the cut is underway. without an offset on Z-home to account for the travel of the floating head, the work position (Z-zero) is wrong. the torch lowers to the work, touches (this is the real zero). Z-axis continues down while the floating head sits on the work until the Z-home switch is made. That distance must be entered into Z-offset in config/homes and limits. Otherwise - the torch will try to start its pierce below the work, but will be interupted by hitting the material before it gets there. well, that's my problem anyway. :-|

jeepsr4ever

Right, your correct you must add the travel from the switch getting triggered to z up and about .100 for the right height for cutting steel. Depending on where you put your switch your actualy Z cut height may vary.

Creepy

Yes, all machines will have a different travel according to where your switch got mounted. I measured the offset by lowering the torch to just touching the material with a bit of .002" feeler gauge, zero'd the Z, then continued moving down until the switch was made. You can then take the Z DRO # and put it in the [config/limits and homes - Z offset] in Mach3. My offset needed to be negative. Sheetcam handles the pierce height and tip gap once the zero is established.

Creepy

ok, ok, wait a sec here...... the post processor ALSO has a Z switch offset right in the code. i was concentrating on getting the Z to home in manual mode. got it to work with the config/limits and switches/z home offset set to my switch travel. then when i was trying to use the DTHC, the dang thing kept zero'ing Z in the wrong spot. the offset mentioned above was not working while running a program created from the DTHC3000 post. The post processor needs to have the switch offset entered! (open it in notepad and its written right there.) looking at the program, it is between the 2 G92's in the Z touch off part of the program. (line 150) so now the Z zero is working good.